Method of stabilizing hydrocarbons



soluble in the hydrocarbons.

Patented Sept. 7, 1948 2,449,010 I MErnon or s'ramuzmo HYDROCARBONS RichardF. Robey, Creator-d. John Fedirko, Elizaboth, and Allan E. Barnett, Westfield, N. J assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 3, 1947, Serial No. 789,574

8 Claims. (Cl. 260-4665) This invention relates to a method of stabilizing hydrocarbon materials and particularly to a method of reducing the peroxide content of hydrocarbons or preventing the formation of peroxides in hydrocarbons whichare exposed to air 01 oxygen.

It is well known that the presence of peroxides in petroleum hydrocarbons of the motor fuel range tends to induce the formation of gumsand to increase the knocking tendencies of motor fuels. Peroxides have also been found to promote deterioration of petroleum lubricating oils, causing bearing corrosion in the absence of oxygen.- It

is also known that the presence of peroxides is particularly undesirable in hydrocarbons of the diolefin type, since the diolefins tend to polymerize comparatively rapidly in. the presence of small quantities of peroxides, whereby rubberl'ike polymers are formed during storage. The present invention relates particularly to the use of additives which materially inhibit the spontaneous formation of peroxides and which will reduce the peroxide content of hydrocarbon materials when the peroxides are already present. The invention is particularly concerned with the reduction of the peroxide content of dioleflns. Studies of the reactions which butadiene, isoprene, cyclopentadiene, the piperylenes, and their higher homologs undergo during'storage and the plant processing indicate that there are two type of polymerization which may take place. One type is the dimerization by a Diels-Adler type condensation, which is bimolecular and homogeneous in the liquid phase under a variety of conditions. The second type of polymerization, the formation of plastic materials of high molecular weight, is more serious since, if such polymerization is-permitted to proceed without control, not only will severe losses of valuable material result both in storage and in operations such as distillation, but

stoppage of equipment will also be caused by solid polymer masses. It has been found that this type of polymerization is catalyzed by peroxides. Peroxides of the diolefins may be formed by air oxidation, and therate of polymerization to plastic substances is related to the peroxide concentration. Certain antioxidants have been found to be quite efiectivein preventing such peroxide formation, the most useful being the antioxidants of the phenolic type which have aliphatic side chains which render the compounds at least moderately In some cases the side chain is not required. For example, ithas been demonstrated that the presence of hydroquinone practically completely prevents appreciable peroxidation of butadiene by air for a concate that the same effect is obtained with iso rene.

It has been found, in accordance with themesent invention, that the antioxidant compound is rendered more effective and will even reduce the concentration of peroxides at a fairly rapid rate i when added to a hydrocarbon already contamii hated by peroxides if a promoter is added which exhibit a standard oxidation potential within the range of about 0.7 to 0. This potential value is measured in volts referred to the hydrogenhydrogen ion couple as zero for uni-t activities at 25 C. Such potentials are tabulated in Handbook of Chemistry and Physics, 25th edition pp. 1333-1334, and correspond to single electrode potentials at 25 C. tabulated in Langes Handbook "0: Chemistry? (1946) pp. 1073-1074.

This application is a continuation-in-part of application Serial No. 537,540, filed May 26, 1944,- in which methylene blue chloride is claimed as the antioxidant promoter. Methylene blue chloride has a standard oxidation potential of -0.53. The present invention is concerned specifically with ionizable metal compound or salt promoters which exhibit standard oxidation potentials between 0 and -0.7, more preferably from 0.04 to -0.53,- including notably titanous, stannous and cuprous salts, which have standard oxidation potentials of -0.04, 0.13, and 0.1'? respectively.

As illustrative of the efiect of peroxides on the polymerization-of diolefins, there will be described 'siderable period, andfurther observations indian investigation in which the polymerization of isoprene to a viscous liquid of rubber-like polymers was studied to observe the quantitative dependence of polymerization rate upon peroxide concentrations.

EXAMPLE -1 Measurements were made of the amount of polymerization of Pure isoprene at o, temperature of 60 C. in the presence of various quantities of the natural peroxide obtained by contactlng isoprene with air. The quantity of peroxide present is indicated by the amount of active ox gen present. The results are shown in Table I.

TABLE I Peroxide catalyzed polymerization of pureispprene at 60 C.

, 9 Active Per Cent 1- Oxygen, g gg Hour To igh B. P. M. o Polymers l 1 Calculated by subtracting rate of dimer formation.

The rate of formation of peroxides by the contact or hydrocarbon with air has been studied.

The opportunities of higher boiling hydrocarbons coming into contact with air in the process of handling in the plant are particularly great. The fact that .the vapor pressures may be less than one atmosphere at ordinary temperature provides Tana! II Rate of perozidation oj is prene by air With re ard to the peroxides. studies have shown that the reduction or peroxides by certain antioxidants used alone is surprisingly low. Tests were made of the rate of peroxide reduction in an aromatic hydrocarbon solution at 80 and 110 C., the reduction in the presence of antioxidant alone being compared with the same amount of antioxidant in combination with (1) methylene blue chloride and (2) stannous chloride.

EXAMPLE 4 Tim Acti o Hrs? cm'ttt i'ff Results of the comparison of effect of tert.- 15 butyl catechol and alpha naphthol on the reduction of tert.-butyl hydroperoxide and isoprene 12 Q3 peroxide in aromatic hydrocarbon solution for t 260 a period of five hours for each test, with and withg; 8% out promoter, are shown in Table IV.

\ TABLE IV Reduction 0 peroxides Vl it S}??- Peroxide l Vessel Reductor I Promoter I. Co t an l a None Nnne hvdmpemlde {Y?fii.iii..fii.f?fiii 'niititniatmsama;ia 0 Such 80 Isoprsne peroxide;

1l0 tert.-Butylhydroperoxide NQHQQIIIIIIIIIIIIIII do tert.-Butyl catcchol-.. None SteeL--- do Metlylene blue chloride o None do Methylene blue chloride tert.-Butyl catechol. None.

1 Initial concentration-100 P. P. M. active oxygen.

EXAMPIE3 Inhibition of the polymerization of isoprene in the presence of natural peroxides was studied at 80 0., using 0.22% alpha naphthol, with and without the presence or methylene blue chloride (0.03%) as a promoter. In all cases the peroxide was present in an amount which provided 100 parts per million 01' active oxygen. Glass vessels were used. The results are shown in Table III.

Tsar: III Inhibition of polymerization of isoprene at 60 C. [In the presence of approx. 100 P. P. M. oi active oxygen] per cent concentration in each case where c= active oxygen concentration in P. P. -M. at time t in hours.

It will be'noted that tert.-butyl catechol was 45 ineffective for reducing the concentration of peroxide during the period of the test, which was five hours, but that rapid reduction was caused by adding an activator in the form of methylene 'blue chloride or stannous chloride. The promoter alone did not cause reduction. A similar effect was observed with alpha naphthol.

The antioxidants which have been found to be most effectively activated by the promoters of the present invention are the phenolic type antioxidants, by which is to be understood not only phenols and alkylated phenols, but also the polyhydroxy benzenes, as well as hydroxylated naphthalenes, such as naphthols. Examples of such antioxidants which are particularly useful are the cresols, catechol, hydroquinone, pyrogallol, the naphthols, and their alkylated derivatives. Since the exact mechanism of the action of the invention is not known, it may find application to other antioxidantsv such as those containing Per cm cm as nitrogen and/or sulfur. substance addedl. gggg zg ggg 111mm. As stated above, the promoters which have- Polymers been used in conjunction with the aforesaid phenolic type antioxidants are compounds exir on g hlbitinga standard oxidation potential between P 0.7 and 0. As examples of these, beside those :53: ch13? d fitfi fk f- 189 0.0041 74 mentioned in Examples 3 and 4, the following are especially mentioned: stannous acetate, other Caleulated by subtracting rate of dimer formation. hydrocarbon soluble stannous salts, titanous at, m gg chloride, and lo'wer oxides of copper, mercurous 'Pemmielnhibiflon-loom chloride, uranous salts, trivalent molybdenum 75 salts and pentavalent molybdenum salts. The

eifect of antioxidants on,

promoter should be present .in an amount equal to at least 10% of the weight of the antioxidant; and the amount of the antioxidant which it is most desirable to use is about twice the theoretical amount required for reduction 01. the peroxide present.

The invention should not be considered as limited by any of the examples which are set forth above for illustrative purposes only, but is to be limited solely by the terms of the appended claims.

We claim:

1. A composition containing a hydrocarbon susceptible toperoxide formation and dissolved therein a small amount of a phenolic type antioxidant with a small amount of a compound of a metal having a standard oxidation potential between 0 and -0.'7.

2. A composition containing a hydrocarbon susceptible to peroxide formation and dissolved therein a small amount of a phenolic type anti oxidant with a small amount of a compound of a metal having a standard oxidation potential from 0.04 to -0.53.

3. A composition containing a diolefln and dissolved therein a phenolic type antioxidant with a small amount of stannous salt.

4. A composition containing a diolefin and dissolved therein a phenolic type antioxidant-with a small amount of stannous chloride.

5. A composition containing isoprene and dis-" solved therein a small amount of tertiary butyl catechol with a small amount of stannous chloride.

6. A composition containing a diolefin and dissolved therein a phenolic type antioxidant with a small amount of a titanous salt.

'7. A composition containing a dioleiin and dissolved therein a phenolic type antioxidant with a small amount of a cuprous compound.

8. The method of reducing the peroxide content of a hydrocarbon material containing a diolefln with a peroxide of the diolefin which tends to cause polymerization of the diolenn comprising the steps of heating said material in the presence of a small amount of a phenolic type antioxidant with a small amount of an antioxidant promoter which is a compound of a metal that exhibits a standard oxidation potential within the limits of the standard oxidation potentials for methylene blue chloride and titanous chloride.

RICHARD F. ROBEY. JOHN FEDIRKO. ALLAN E. BARNETT. 

